Methods for improving jet cutting performance via force sensing

ABSTRACT

Disclosed herein are systems and methods for improving the performance of a fluid jet cutting system by testing and adjusting characteristics of the system based on the effect of the characteristics on forces imparted by the system to a workpiece being cut. Also disclosed are systems and methods for monitoring and validating the performance of fluid jet cutting systems, and for diagnosing such systems. In some cases, the technologies described herein can be used to determine whether components of a fluid jet system require maintenance, or that characteristics of the system require adjustment.

BACKGROUND Technical Field

This disclosure relates to systems and methods for improving theperformance of fluid jet cutting systems, and more particularly tosystems and methods for improving the performance of fluid jet cuttingsystems by testing and adjusting characteristics of the fluid jetcutting system based on forces imparted by the system to a sample havingcharacteristics (e.g., material type, material thickness) the same as orsimilar to a workpiece to be cut.

Description of the Related Art

High-pressure fluid jets, including high-pressure abrasive fluid jets,are used to cut a wide variety of materials in many differentindustries. Abrasive fluid jets have proven to be especially useful incutting difficult, thick, or aggregate materials, such as thick metal,glass, or ceramic materials. Systems for generating high-pressureabrasive fluid jets are currently available, such as, for example, theMach 4 5-axis abrasive fluid jet system manufactured by FlowInternational Corporation, the assignee of the present invention, aswell as other systems that include an abrasive fluid jet cutting headassembly mounted to an articulated robotic arm. Software for controllingsuch systems is currently available, such as, for example, theFlowMaster™ fluid jet system also available from Flow. Other examples ofabrasive fluid jet cutting systems are shown and described in Flow'sU.S. Pat. No. 5,643,058, which is incorporated herein by reference.

The terms “high-pressure fluid jet” and “jet” should be understood toincorporate all types of high-pressure fluid jets, including but notlimited to, high-pressure waterjets and high-pressure abrasivewaterjets. In such systems, high-pressure fluid, typically water, flowsthrough an orifice in a cutting head to form a high-pressure jet, intowhich abrasive particles are combined as the jet flows through a mixingtube. The high-pressure abrasive fluid jet is discharged from the mixingtube and directed toward a workpiece to cut the workpiece along adesignated path. In some cases, the designated path and characteristicsof the fluid jet are controlled by software running on a computersystem, as further described below.

Various systems are currently available to move a high-pressure fluidjet along a designated path. Such systems may commonly be referred to,for example, as three-axis and five-axis machines. Conventionalthree-axis machines mount the cutting head assembly in such a way thatit can move along an x-y plane and perpendicular along a z-axis, namelytoward and away from the workpiece. In this manner, the high-pressurefluid jet generated by the cutting head assembly is moved along thedesignated path in an x-y plane, and is raised and lowered relative tothe workpiece, as may be desired. Conventional five-axis machines workin a similar manner but provide for movement about two additionalnon-parallel rotary axes. Other systems may include a cutting headassembly mounted to an articulated robotic arm, such as, for example, a6-axis robotic arm which articulates about six separate rotary axes.

Computer-aided manufacturing (CAM) processes may be used to efficientlydrive or control such conventional machines along a designated path,such as by enabling two-dimensional or three-dimensional models ofworkpieces generated using computer-aided design (i.e., CAD models) tobe used to generate code to drive the machines. For example, a CAD modelmay be used to generate instructions to drive the appropriate controlsand motors of the machine to manipulate the machine about itstranslational and/or rotary axes to cut or process a workpiece asreflected in the model.

The performance of a fluid jet cutting system depends on manycharacteristics of the system, including the size of a jet orifice ofthe cutting system, the pressure developed within the cutting systembehind the orifice, the type, mesh size, and flow rate of abrasive(s)that may be introduced into the jet, the size of a mixing tube ordischarge nozzle of the cutting system, the speed at which the jet istranslated across the workpiece, etc. In some cases, the performance ofa fluid jet cutting system can be characterized in terms of the qualityof the cut formed in the workpiece by a fluid jet of the cutting system,defined in some cases in terms of the roughness, planarity, orconsistency of the surface of the workpiece exposed by the cut.

Assessing the quality of a cut formed in a workpiece can be a difficult,time-consuming, expensive, and inexact task. Typically, such anassessment requires that a skilled technician inspect the exposedsurface of the workpiece at the cut to provide a qualitative assessmentor estimate of the quality of the cut. Devices such as profilometers canbe used but do not provide the reliability or accuracy offered byembodiments of the technologies described herein. Thus, in order to testor adjust a characteristic of a cutting system affecting jetperformance, such as one of those listed above, a technician musttypically make several cuts in a workpiece while varying acharacteristic of interest, and inspect the exposed surfaces of each ofthe several cuts to determine which may be associated with the bestperformance. This process is prone to errors and can be extremelylaborious and time-consuming, and can result in extended periods ofmachine downtime.

BRIEF SUMMARY

Embodiments described herein can be used to improve the performance of afluid jet cutting system by evaluating or modifying characteristics ofthe system based on forces imparted by a jet generated by the system toa sample having characteristics (e.g., material type, materialthickness) the same as or representative of a workpiece to be cut.

In some cases, a method of improving fluid jet performance comprisesselecting a first setting for a characteristic of a fluid jet system,forming a first cut in a coupon of material using the fluid jet systemhaving the first setting for the characteristic, while forming the firstcut in the coupon, measuring a first history of reactive forces impartedby the fluid jet system to the coupon during at least a portion of thefirst cut, selecting a second setting for the characteristic of thefluid jet system, forming a second cut in the coupon using the fluid jetsystem having the second setting for the characteristic, while formingthe second cut in the coupon, measuring a second history of reactiveforces imparted by the fluid jet system to the coupon during at least aportion of the first cut, designating the first setting as a preferredor optimal setting if an average or typical value of the first historyof reactive forces is lower than an average or typical value of thesecond history of reactive forces and a quality of the first cut isacceptable, and designating the second setting as an optimal setting ifthe average or typical value of the second history of reactive forces islower than the average or typical value of the first history of reactiveforces and a quality of the second cut is acceptable.

In some cases, a method of assessing performance of a fluid jet systemcomprises situating a workpiece at least partially within a workingenvelope of a cutting head of a fluid jet cutting system to be cut bythe cutting head, situating a coupon at least partially within theworking envelope of the cutting head of the fluid jet cutting system tobe cut by the cutting head, forming one or more cuts in the workpieceusing the cutting head of the fluid jet cutting system, periodicallyinterrupting the forming of the one or more cuts in the workpiece,during at least one of the periodic interruptions, forming a sample cutin the coupon using the cutting head of the fluid jet cutting system,while forming the sample cut in the coupon, measuring a history ofreactive forces imparted by the fluid jet cutting system to the coupon,and using the measured reactive forces to assess the performance of thefluid jet cutting system.

In some cases, a method of establishing a working speed comprisesforming a plurality of cuts in a coupon using a fluid jet system, eachof the plurality of cuts being formed while moving a cutting head of thefluid jet system at a different speed, while forming the plurality ofcuts in the coupon, measuring a corresponding history of reactive forcesimparted by the fluid jet system to the coupon for each of the pluralityof cuts, computing an average or typical reactive force for eachcorresponding history of reactive forces, designating a first speedcorresponding to an average or typical reactive force approximating athreshold allowable force as a preferred or optimal speed, designating asecond speed corresponding to the preferred or optimal speed reduced byan offset percentage as an initial working speed, and forming one ormore cuts in a workpiece remote from the coupon using the cutting headof the fluid jet system while moving the cutting head at the initialworking speed.

In some cases, a method of assessing performance of a fluid jet systemcomprises, prior to forming one or more cuts in a workpiece with acutting head of a fluid jet cutting system, forming a baseline cut in acoupon using the fluid jet system while moving the cutting head at aninitial working speed, while forming the baseline cut, measuring acorresponding baseline history of reactive forces imparted by the fluidjet system to the coupon, periodically interrupting the forming of theone or more cuts in the workpiece, during at least one of the periodicinterruptions, forming a validation cut in the coupon using the fluidjet system while moving the cutting head at the initial working speed,while forming the validation cut, measuring a corresponding validationhistory of reactive forces imparted by the fluid jet system to thecoupon, and comparing the validation history of reactive forces to thebaseline history of reactive forces to assess the performance of thefluid jet system.

In some cases, a fluid jet cutting system comprises a fluid jet cuttinghead, a motion system for manipulating the fluid jet cutting head inspace within a working envelope, a coupon platform positioned at leastpartially within the working envelope, and a force measuring deviceoperatively coupled to the coupon platform to measure forces applied tothe coupon platform by a fluid jet discharged from the fluid jet cuttinghead via the intermediary of a coupon of material positioned on thecoupon platform.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a top isometric view of a fluid jet cutting systemincluding a validation system.

FIG. 1A illustrates an enlarged detail view of the validation systemshown in FIG. 1.

FIG. 2 illustrates a side view of the fluid jet system of FIG. 1.

FIG. 3 illustrates a side view of a cutting head of the fluid jet systemof FIGS. 1 and 2.

FIG. 4 illustrates a top plan view of a portion of the validation systemshown in FIGS. 1 and 1A.

FIG. 5 illustrates a side view of the portion of the validation systemshown in FIG. 4.

FIG. 6 illustrates a plurality of cuts formed in a coupon of materialusing a fluid jet cutting system while moving a cutting head of thefluid jet system at different speeds.

FIG. 7 illustrates a relationship between cutting head translation speedand resulting reactive forces imparted by a fluid jet on a sample orcoupon of material.

FIG. 8 illustrates a relationship between abrasive flow rate of anabrasive fluid jet system and resulting reactive forces imparted by anabrasive fluid jet on a sample or coupon of material.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails. In other instances, well-known structures and controltechniques associated with fluid jet cutting machines or othermulti-axis machines may not be shown or described in detail to avoidunnecessarily obscuring descriptions of the embodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, such as“comprises” and “comprising,” are to be construed in an open, inclusivesense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contextclearly dictates otherwise. Embodiments of the methods and systemsdescribed herein can be used to improve fluid jet cutting systemperformance, such as by facilitating the testing, evaluation,adjustment, improvement, calibration, or optimization of characteristicsof the system. Although some aspects discussed herein may be discussedin terms of waterjets and abrasive waterjets, one skilled in therelevant art will recognize that aspects and techniques of the presentinvention can be applied to any type of fluid jet, generated by highpressure or low pressure, whether or not additives or abrasives areused.

FIGS. 1, 1A, and 2 show an example embodiment of a fluid jet cuttingsystem 10. The fluid jet cutting system 10 includes a catcher tankassembly 12 which is configured to support a workpiece 14 to beprocessed by the system 10, such as on supporting elements such as slats16. “Workpiece,” as used herein, can refer to a single one or aplurality of such elements. The fluid jet cutting system 10 furtherincludes a bridge assembly 18 which is movable along a pair of baserails 20 and straddles the catcher tank assembly 12. In operation, thebridge assembly 18 moves back and forth along the base rails 20 withrespect to a translational axis X to position a cutting head 22 of thesystem 10 for processing the workpiece 14. A tool carriage 24 is movablycoupled to the bridge assembly 18 to translate back and forth alonganother translational axis Y, which is aligned perpendicularly to thetranslational axis X. The tool carriage 24 is further configured toraise and lower the cutting head 22 along yet another translational axisZ to move the cutting head 22 toward and away from the workpiece 14. Anarticulated forearm and wrist assembly 26 is provided to adjust anorientation of the cutting head 22 relative to the workpiece 14 toenable processing of the workpiece 14 along particularly complex toolpaths and tool orientations. During operation, movement of the cuttinghead 22 with respect to each of the translational axes X, Y, Z and axesof the articulated forearm and wrist assembly 26 may be accomplished byvarious conventional drive components and an appropriate control system28, which can include a controlling computer system, as furtherdescribed below.

A waste removal system 30 may be coupled to the catcher tank assembly 12to receive and process waste collected from the interior of the catchertank assembly 12 during operation. Other well-known systems associatedwith fluid jet cutting machines may also be provided such as, forexample, a high-pressure or ultrahigh-pressure fluid source 27 (FIG. 3),which may be a direct drive or intensifier pump with a pressure ratingranging from about 20,000 psi to 100,000 psi and higher, for supplyinghigh-pressure or ultrahigh-pressure fluid to the cutting head 22, and/oran abrasive source 29 (FIG. 3), such as an abrasive hopper anddistribution system, for feeding abrasives to the cutting head 22 toenable abrasive fluid jet cutting. In some embodiments, a vacuum device31 (FIG. 3) may also be provided to assist in drawing abrasives into thefluid from the fluid source to produce a consistent abrasive fluid jetto enable particularly accurate and efficient workpiece processing.Details of the control system 28, conventional drive components andother well-known systems associated with fluid jet cutting systems,however, are not shown or described in detail to avoid unnecessarilyobscuring descriptions of the embodiments.

FIG. 3 shows the cutting head 22 in operation. The cutting head 22includes a mixing tube or nozzle 40, from which a jet 42 exits at highspeed. In some cases, the jet 42 is an abrasive fluid jet including afluid such as water mixed with abrasive particles. FIG. 3 shows that thecutting head 22 can be situated above the workpiece 14, such that thenozzle 40 and jet 42 extend downward toward the workpiece 14, and suchthat the jet 42 approaches the workpiece 14 along an axis generallyperpendicular or slightly inclined relative to an upper surface of theworkpiece 14. As the cutting head 22 is operated to direct the jet 42toward the workpiece 14 to cut the workpiece 14, the cutting head can bemoved laterally over the workpiece 14 in a travel direction T (e.g.,along one or both of the translational axes X, Y) so as to cut theworkpiece 14 along a designated path. FIG. 3 shows a surface 32 of theworkpiece 14 exposed by the cutting action of the jet 42, and an un-cutportion 34 of the workpiece 14.

Cutting of the workpiece 14 is accomplished by the impact of, and thecorresponding force imparted by, the jet 42 against the workpiece 14. Insome cases, as the cutting head 22 moves laterally to cut the workpiece14, a cutting surface 36 at the leading edge of the cut becomes curved,such that the exposed surface 32 extends farther in the travel directionat the top of the cut than at the bottom of the cut. The degree of thiscurvature can be influenced by the thickness of the workpiece. Forexample, the cutting surface of a relatively thick workpiece typicallyhas a greater curvature than the cutting surface of a relatively thinworkpiece. This curvature occurs as a result of a phenomenon known as“tailback” or “drag,” as shown and described in more detail in U.S. Pat.No. 6,766,216 (see, e.g., background section and FIG. 2 thereof), whichis hereby incorporated herein by reference in its entirety. As a resultof this curvature, the force imparted by the jet 42 to the workpiece 14is not necessarily entirely vertical. In some cases, the force F_(j)imparted by the jet 42 to the workpiece 14 has a vertical componentF_(v) and a horizontal component F_(h).

While not being bound by any particular mode of action, it is believedthat a curvature of the cutting surface 36 and other aspects of theresulting edges and faces of the workpiece adjacent the cut are afunction of a variety of characteristics of the system 10. Further, itis believed that a greater curvature of the cutting surface 36 iscorrelated with rougher exposed surfaces at the cut, e.g., surface 32.Thus, in some cases, the degree of the curvature of the cutting surface36, or the amount by which the exposed surface 32 extends farther in thetravel direction at the top of the cut than at the bottom of the cut,can be used in the various embodiments described herein as indicative ofcut quality.

Further still, a greater curvature of the cutting surface 36 iscorrelated with higher forces F_(v) and F_(h) (and thus F_(j)) impartedby the jet 42 to the workpiece 14. Thus, in various embodimentsdescribed herein, the effect of a characteristic of the system 10 on theforces F_(v), F_(h), and/or F_(j) imparted by the jet 42 to theworkpiece 14 are studied to assess the effect of that characteristic onthe performance of the system 10 and the quality of cuts formed in theworkpiece 14 by the jet 42 of the system 10. In some cases, preliminarystudies can be conducted to assess and/or quantify a relationshipbetween one or more of the forces F_(v), F_(h), F_(j), and cut qualityfor a variety of materials, such that for any specified material and cutquality, a corresponding force F_(v), F_(h), and/or F_(j) may begenerally known. These corresponding forces can then be used in thevarious embodiments described herein as indicative of cut quality, forexample.

With reference to FIGS. 1A, 4 and 5, and in accordance with someembodiments, the system 10 can include a validation system 38, which canbe used to test, evaluate, adjust, improve, or optimize one or morecharacteristics of the system 10. As shown in top and side views inFIGS. 4 and 5, respectively, the validation system 38 can include aforce measurement device 44, which in some cases may be a forcedynamometer including a horizontal force transducer and a vertical forcetransducer. The validation system 38 can also include a base plate 46having a plurality of fingers or other support structures 48 separatedby a plurality of clearance slots 50. The base plate 46 can be rigidlycoupled to the force measurement device 44 so that forces (verticaland/or horizontal) imparted to the base plate 46 can be measured by theforce measurement device 44. The validation system 38 may be configuredto receive and support a sample or coupon 52, which can comprise arelatively small piece of material having material and othercharacteristics (e.g., thickness) substantially matching that of, orrepresentative of, a workpiece 14 to be cut by the system 10. “Sample”or “coupon,” as used herein, can refer to a single one or a plurality ofsuch elements. In some instances, the sample or coupon 52 may consist ofan actual piece of material removed from the workpiece 14 to beprocessed. Forces imparted to the sample or coupon 52 by the jet 42discharged from nozzle or mixing tube 40 can be treated as generallyrepresentative of forces expected to be imparted to the workpiece 14 bythe jet 42 during actual cutting of the workpiece 14 remote from thesample or coupon 52. The sample or coupon 52 can be rigidly coupled orfixed to the base plate 46 such that forces imparted to the sample orcoupon 52 are transferred to the base plate 46, such as, for example,via a clamp or other attachment device (not shown).

The validation system 38 can be situated within and/or coupled to thecatcher tank assembly 12 (FIGS. 1, 1A, and 2) so that the system 10 canbe used to cut the sample or coupon 52, in a manner similar to thatdescribed above for the workpiece 14. For example, the validation system38 can be mounted to a side of the catcher tank assembly 12, or on astand 60 within the catcher tank assembly 12. In other instances, thevalidation system 38 can be mounted near or adjacent to the catcher tankassembly 12 or a different workpiece support system, but nevertheless atleast partially within a working envelope of the fluid jet cuttingsystem 10 such that the cutting head 22 can make cuts on the sample orcoupon 52 prior to, during or after making one or more cuts on theworkpiece 14.

The validation system 38 can be coupled to the control system 28 by acommunications link 62, and to the controlling computer system, whichcan receive one or more signals from the force measurement device 44,such as a signal corresponding to a measured horizontal force, a signalcorresponding to a measured vertical force, and/or a combinationthereof.

Some embodiments described herein include the measurement of variousforces, such as forces F_(j), F_(h), or F_(v) imparted by the jet 42 tothe sample or coupon 52. Many different techniques can be used tomeasure one or more such forces. For example, the measurement device 44can measure these forces either continuously, generating, e.g., ananalog response signal, or discontinuously, at any one of a wide rangeof frequencies, generating, e.g., a digital response signal. The datagenerated by the measurement device 44 can be recorded and/or analyzedby the computer system to provide an average or typical orrepresentative force measurement.

In some cases, an average force measurement can be calculated as themean, the median, or the mode of the data generated by the measurementdevice 44. In some cases, an average force measurement can be calculatedas a weighted average of the data generated by the measurement device44, for example, by weighting measurements taken during a middle portionof a cut more heavily than measurements taken during other portions ofthe cut. In some cases, an average force measurement can be calculatedbased on a history of reactive forces imparted by the jet 42 to thesample or coupon 52 during an entire cut, while in other cases, theaverage can be calculated based on a history of reactive forces impartedby the jet 42 to the sample or coupon 52 during only a portion of thecut.

In some cases, a typical force measurement can be determined by atechnician based on a review of the data generated by the measurementdevice 44, for example, as an estimate of an average of the data. Insome cases, a representative force measurement can be an average forcemeasurement, a typical force measurement, or any other force measurementrepresentative or characteristic of the data generated by themeasurement device 44. In some cases, a force measurement at apredetermined time can be considered a representative force measurement,e.g., a force measurement taken at the half-way point of a cut can beconsidered representative of the forces imparted by the jet 42 to thesample or coupon 52.

In some embodiments, the system 10 can be used to form a plurality ofcuts in the sample or coupon 52, such as at locations corresponding tothe clearance slots 50 such that only the interaction of the jet 42 withthe sample or coupon 52 causes resultant forces measured by the forcemeasurement device 44. In some cases, in order to assess the effect of acharacteristic on the performance of the system 10, the characteristiccan be varied while forming the plurality of cuts in the sample orcoupon 52. As one example, to assess the effect of the speed of thetranslation of the cutting head 22 across the sample or coupon 52, thesystem 10 can be used to form a first cut in the sample or coupon 52while the cutting head 22 is translated at a first rate, such as, forexample, 0.2 mm/s, a second cut in the sample or coupon 52 while thecutting head 22 is translated at a second rate, such as, for example,0.4 mm/s, and a third cut in the sample or coupon 52 while the cuttinghead 22 is translated at a third rate, such as, for example, 0.8 mm/s.All other characteristics of the cutting system 10 can be held constantduring this process in order to isolate the effect of the translationspeed on system cutting performance.

The plurality of cuts can be formed in the sample or coupon 52 while thesample or coupon 52 is supported by the validation system 38 describedabove. Thus, the forces imparted to the sample or coupon 52 during theformation of each of the cuts can be measured, and represented by dataprocessed and/or stored in the computer system, as described elsewhereherein. In some cases, the data representing the forces can be stored asit is recorded, while in other cases, some pre-processing can beconducted on the data before it is stored. For example, the datarepresenting the forces can be divided by another, baseline force, suchas a maximum force, such that the stored data represents the forcesnormalized by the baseline force. Based on the resulting measuredforces, a preferred, optimal, or improved translation speed can beascertained or established. For example, the data can be analyzed todetermine a force or force range at which cut quality transitionsbetween acceptable and non-acceptable quality standards, and thetranslation speed associated with the force or force range can beestablished as an optimal or improved translation speed. In someinstances, a rate of change of the detected force may be used todetermine the optimal or improved translation speed. This process can beused to ascertain or establish optimal or improved values, choices,properties, or settings for a variety of characteristics of the system10, including any of those described herein.

In some cases, forces imparted by the jet 42 to the workpiece 14 or thecoupon 52 can be different in cases in which the jet 42 is used toinitiate a cut into the workpiece 14 or the coupon 52 than in cases inwhich the jet 42 is used to continue an initiated cut through theworkpiece 14 or coupon 52. Further, forces imparted by the jet 42 to theworkpiece 14 or the coupon 52 can be different in cases in which the jet42 is used to initiate a cut into a side of the workpiece 14 or thecoupon 52 than in cases in which the jet 42 is used to initiate a cutinto a center region of the workpiece 14 or the coupon 52 (that is,pierce the workpiece 14 or coupon 52). Unless specified otherwise,measurements of forces such as F_(j), F_(h), or F_(v) are conducted whenthe jet 42 is “fully engaged,” that is, used to continue a cut byentering a top surface of the workpiece 14 or coupon 52, exiting abottom surface of the workpiece 14 or coupon 52, and cutting (e.g.,removing material from) the workpiece 14 or coupon 52.

In alternative embodiments, however, measurements can be conducted asthe jet 42 is “partially engaged,” that is, used to initiate a cut intothe workpiece 14 or coupon 52, such as to ascertain or establish optimalor improved values, choices, properties, or settings for variouscharacteristics of the system 10 for use in initiating a cut into theworkpiece 14 or coupon 52. In cases in which the jet 42 is partiallyengaged, measured forces can vary non-linearly as the jet 42 moves withrespect to the workpiece 14 or coupon 52.

FIGS. 6 through 8 show examples of results of such assessments. Inparticular, FIG. 6 shows a bottom portion of a coupon 54 and a pluralityof cuts 56 formed by a fluid jet cutting system in the coupon 54. Cut56A formed in a left portion of the coupon 54, as shown in FIG. 6, wasformed while moving the cutting head 22 at a relatively slow speed,while cut 56B formed in a right portion of the coupon 54, as shown inFIG. 6, was formed while moving the cutting head 22 at a relatively fastspeed. Each of the cuts 56 between cut 56A and cut 56B was formed whilemoving the cutting head at a different speed, which increasedsuccessively for each of the cuts 56 from cut 56A to cut 56B. In someinstances, the speeds may be increased in regular intervals, and inother instances, may be increased in irregular intervals. In addition,it is appreciated that the cuts can be made at successively decreasingspeeds or at otherwise varying speeds provided that a significantsampling of cuts at different speeds is made.

As shown in FIG. 6, the quality of the cuts 56 generally degrades as thetranslation speed increases. This relationship is further illustrated bythe data shown in FIG. 7, which plots translation speed of the cuttinghead 22 on the horizontal axis against the force measured by a forcemeasurement device 44 of a validation system 38 on the vertical axis. Asshown in FIG. 7, as translation speed of the cutting head 22 increases,so does the measured force (albeit at a non-linear rate) consideringthat the jet is fully engaged with the material (i.e., jet passescompletely through the coupon) in all tests. Because measured forces arebelieved to be generally inversely correlated with cut quality, asexplained above, the data presented in FIG. 7 generally reflects theresults shown in FIG. 6.

In some cases, a predetermined threshold value for the slope (i.e.,instantaneous rate of change) of a curve such as the curve illustratedin FIG. 7 can be used to select an optimal or improved translationspeed. For example, a predetermined threshold value for the slope of thecurve of FIG. 7 can represent an upper limit on the degree to which cutquality can be sacrificed in the interest of increased cutting speed.Thus, the translation speed associated with the occurrence of thethreshold value for the slope can be established or designated as anoptimal or improved translation speed.

In other cases, a predetermined threshold value for the measured forcecan be used to select an optimal or improved translation speed. Forexample, a predetermined threshold value for the measured force canrepresent a lower limit on the quality of an acceptable cut. Thus, thetranslation speed associated with the occurrence of the threshold valuefor the measured force can be established or designated as an optimal orimproved translation speed. In some cases, the occurrence of thethreshold value for the measured force can correspond to a thresholdvalue for the slope, as described above.

As an example, FIG. 7 shows the location of an optimal translation speedv_(o) on the curve, which corresponds to a threshold or optimal forcef₀₁, the threshold value for the slope of the curve, and an optimal cut56C. In some instances, cutting operations can be performed on aworkpiece 14 generally corresponding to the coupon 54 while moving thecutting head 22 at a rate within an acceptable range of rates, that is,at a rate within a range V_(r), such as within the rate V_(o) plus orminus an acceptable variance percentage (e.g., V₀±5% or V₀±10%).

In some cases, the translation speed associated with the occurrence ofthe threshold value for the slope or for the measured force can be atranslation speed corresponding to a measured reactive force mostclosely approximating the respective predetermined threshold value. Insome cases, the translation speed associated with the occurrence of thethreshold value for the slope or for the measured force can be atranslation speed corresponding to a measured reactive force less thanthe respective predetermined threshold value. In some cases, thetranslation speed used to cut a workpiece can be less than thedesignated optimal translation speed. For example, the translation speedused to cut a workpiece can be 95% of the designated optimal or“maximum” speed, or 90%, or 85%, or 80%, or 75%, or 70% of thedesignated optimal or “maximum” speed. The degree by which thetranslation speed used to cut a workpiece deviates from the designatedoptimal or “maximum” translation speed can be controlled using controlsoftware (e.g., FlowMaster™ control software or other software) runningon the computer system, the control system 28, or by other means.

FIG. 8 illustrates data similar to that illustrated in FIG. 7, but forthe characteristic of abrasive flow rate (i.e., rate at which abrasivesare fed into a fluid jet stream to form an abrasive fluid jet) ratherthan cutting head translation speed. As shown in FIG. 8, the dataillustrates that measured forces decreased as the abrasive flow rateincreased to a transition point 58, after which the measured forcesincreased as the abrasive flow rate increased. In some cases, theabrasive flow rate associated with the transition point 58 is consideredor can be established as an optimal abrasive flow rate. As an example,FIG. 8 shows the location of an optimal abrasive flow rate AFR₀ on thecurve, which corresponds to a threshold or optimal force f₀₂ and thetransition point 58. In some instances, cutting operations can beperformed on a workpiece 14 generally corresponding to the coupon 54while feeding abrasive material(s) into the cutting head 22 at a ratewithin an acceptable range of rates, that is, at a rate within a rangeAFR_(r), such as within the rate AFR_(o) plus or minus an acceptablevariance percentage (e.g., AFR₀±5% or AFR₀±10%).

Such assessments can be conducted for a variety of characteristics ofthe system 10. For example, a plurality of cuts can be formed in asample or coupon 52 while varying any one of the characteristicsdescribed herein. The forces imparted to the sample or coupon 52 duringthe formation of the cuts can be measured and analyzed to ascertain orestablish an optimal or improved value, choice, property, or setting forthe characteristic. Such techniques offer consistent and reliablequantitative assessments of cut quality and the effect of systemcharacteristics on cut quality.

In some embodiments, the validation system 38 can be used to monitor andvalidate the performance of the system 10. For example, the system 10can be set up such that all characteristics have settings matching thoseto be used to cut the workpiece 14. The system 10 can then be used tocut the sample or coupon 52 and the resulting reactive forces can bemeasured and designated as baseline reactive forces. The system 10 canthen be used to cut the workpiece 14, and as the system 10 is used tocut the workpiece 14, the forces imparted by the jet 42 to the workpiece14 can be monitored, such as by any suitable measuring device(s).Measurements of the reactive forces can be taken periodically orcontinually. In other cases, as the system 10 is used to cut theworkpiece 14, the cutting of the workpiece 14 can be periodicallyinterrupted so the system 10 can be used to cut the sample or coupon 52or a different sample or coupon of the same or similar makeup, and theforces imparted by the jet 42 to the sample or coupon 52 can be measuredand considered representative of the forces imparted by the jet 42 tothe workpiece 14, such that the forces imparted by the jet 42 to theworkpiece 14 need not be measured directly. As examples, measurements ofthe reactive forces imparted to the coupon 52 can be taken betweensuccessive cuts formed in the workpiece 14, between forming cuts insuccessive parts of the workpiece 14, or at pre-determined intervalsbased on the geometry of the cuts to be formed in the workpiece 14, forexample. In cases in which cutting of the workpiece 14 is periodicallyinterrupted so the system 10 can be used to cut the sample or coupon 52,the sample or coupon 52 can have characteristics matching orrepresentative of the characteristics of the workpiece 14, or can havecharacteristics that do not match and are not representative of theworkpiece 14.

A deviation of the measured reactive forces from the baseline reactiveforces can indicate that a change in one or more of the characteristicsof the system 10 is warranted. In some cases, one or more of thecharacteristics can be adjusted in response to such a deviation, inorder to reduce or eliminate the deviation. For example, if the measuredreactive forces are found to be less or greater than the baselinereactive forces, then the translation speed of the cutting head can beadjusted (e.g., at initial system set-up or in real time duringoperation) to compensate accordingly. As another example, if themeasured reactive forces are found to be greater or less than thebaseline reactive forces, then the abrasive flow rate can be adjusted(e.g., at initial system set-up or in real time during operation) tocompensate accordingly. In some cases, a deviation of the measuredreactive forces from the baseline reactive forces by a predeterminedthreshold can indicate that a change in one or more of thecharacteristics of the system 10 is warranted. In some cases, thepredetermined threshold can be about 1%, 2%, 5%, 10%, 15%, 20%, 25%, or50%.

In some embodiments, the validation system 38 can be used as adiagnostic tool for the system 10. For example, measured reactive forcescan be compared to baseline reactive forces, as described above. Adeviation of the measured reactive forces from the baseline reactiveforces by a predetermined threshold can indicate that a component of thesystem 10 is worn, fouled, broken, malfunctioning, or otherwise requiresmaintenance, or should be replaced. For example, a deviation of themeasured reactive forces from the baseline reactive forces by greaterthan 10% may indicate that the mixing tube of the system 10 hasundergone a significant amount of wear and should be replaced.

As another example, prior to cutting the workpiece 14, the system 10 canbe set up such that the abrasive flow rate is zero, so the jet 42includes no abrasive materials. The system 10 can then be used to directthe jet 42 at the base plate 46 with or without the coupon 52 situatedthereon, and the resulting reactive forces can be measured anddesignated as baseline fluid-only reactive forces. The abrasive flowrate can then be set to a working abrasive flow rate and the system 10can be used to cut the workpiece 14. Cutting of the workpiece 14 can beperiodically interrupted so the abrasive flow rate can be set to zero,the system 10 can be used to direct the jet 42 to the base plate 46, andthe forces imparted by the jet 42 to the base plate 46 can be measuredand designated as measured fluid-only reactive forces. A deviation ofthe measured fluid-only reactive forces from the baseline fluid-onlyreactive forces can be indicative of a degree of wear to or the healthof the orifice of the system 10, for example. Deviation of the measuredfluid-only reactive forces from the baseline fluid-only reactive forcesby a predetermined threshold can indicate that the orifice requiresmaintenance or replacement. Upon such an indication that the orificerequires maintenance or replacement, the cutting head 22 can be removedfrom the system 10 for inspection, maintenance, etc.

As another example, the system 10 can be set up such that allcharacteristics have given validation settings. The system 10 can thenbe used to pierce the coupon 52 and the resulting reactive forces,changes in reactive forces over the course of the piercing process, andtime taken to pierce the coupon 52 can be measured and designated asbaseline piercing values. The characteristics can then be set to workingsettings and the system 10 can be used to cut the workpiece 14. Cuttingof the workpiece 14 can be periodically interrupted so thecharacteristics have the given validation settings, the system 10 can beused to pierce the coupon 52, and the resulting reactive forces, changesin reactive forces, and time taken to pierce the coupon 52 can bemeasured and designated as measured piercing values. Deviation of themeasured piercing values from the baseline piercing values can indicatethat a change in one or more of the characteristics of the system 10 iswarranted. In some cases, one or more of the characteristics can beadjusted in response to such a deviation, in order to reduce oreliminate the deviation. In some cases, deviation of the measuredpiercing values from the baseline piercing values by a predeterminedthreshold can indicate that a component of the system 10 is worn,fouled, broken, malfunctioning, or otherwise requires maintenance, orshould be replaced.

As another example, the system 10 can be used to determine amachinability index with the aid of the coupon 52 and the validationsystem 38. For example, as described above, preliminary studies can beconducted to assess and/or quantify a relationship between one or moreof the forces F_(v), F_(h), F_(j), and cut quality for a variety ofmaterials, such that for any specified material and cut quality, acorresponding force F_(v), F_(h), and/or F_(j) is known. A machinabilityindex for each of the materials studied can be computed or determinedfrom the associated relationship between the one or more reactive forcesand the cut quality. That is, the higher the cut quality for a givenmaterial and given reactive force(s), the higher the material'smachinability index is.

As another example, the system 10 can be used to measure an angle ofinclination of the jet 42. For example, the system 10 can be used todirect the jet 42 toward an upper surface of the coupon 52 whilemaintaining the position of the cutting head 22, and to record theresulting horizontal and vertical reactive forces, as described above.By comparing the measured horizontal and vertical reactive forces, theangle of inclination of the jet 42 with respect to the upper surface ofthe coupon 52 can be determined.

In some cases, this technique can be used to calibrate the inclinationof the jet 42. For example, a user can instruct the computer system toorient the nozzle 40 to be generally perpendicular to the upper surfaceof the coupon 52. The system 10 can then be used to measure the angle ofinclination as described above. The measured angle of inclination canrepresent a misalignment of the nozzle 40 and can be compensated for byappropriate adjustment of the system 10.

Any of the components of the fluid jet systems described herein can becontrolled by one or more computer systems, either directly or throughthe control system 28, as described above. Similarly, any of themeasurements and data referred to herein can be collected, stored, andanalyzed by the computer system(s). A computer system may generallyinclude, without limitation, one or more computing devices, such asprocessors, microprocessors, digital signal processors (DSP),application-specific integrated circuits (ASIC), and the like. To storeinformation, a computer system may also include one or more storagedevices, such as volatile memory, non-volatile memory, read-only memory(ROM), random access memory (RAM), and the like. The storage devices canbe coupled to the computing devices by one or more buses. A computersystem may further include one or more input devices (e.g., displays,keyboards, touchpads, controller modules, or any other peripheraldevices for user input) and output devices (e.g., displays screens,light indicators, and the like). A computer system can store one or moreprograms for processing any number of different workpieces according todesignated paths.

A computer system may include multiple interacting computing systems ordevices, and the computer system may be connected to other devices,including through one or more networks, such as the Internet. Moregenerally, a computing device or other computing system may comprise anycombination of hardware or software that may interact and perform thedescribed types of functionality, including without limitation, desktopor other computers, database servers, network storage devices and othernetwork devices. In addition, the functionality provided by the computersystem may in some embodiments be distributed in various softwaremodules. Similarly, in some embodiments some of the functionality of thecomputer system may not be provided and/or other additionalfunctionality may be available.

Software running on the computer system can be stored in memory whilebeing used, or can be transferred between memory and other storagedevices for purposes of memory management and data integrity.Alternatively, in other embodiments some or all of the software modulesand/or systems may execute in memory on another device and communicatewith the computer system via inter-computer communication. Furthermore,in some embodiments, some or all of the systems and/or modules may beimplemented or provided in other manners, such as at least partially infirmware and/or hardware. Some or all of the modules, systems and datastructures may also be stored (e.g., as software instructions orstructured data) on a computer-readable medium, such as a hard disk, amemory, a network, or a portable media article to be read by anappropriate drive or via an appropriate connection. The systems, modulesand data structures may also be transmitted as generated data signals(e.g., as part of a carrier wave or other analog or digital propagatedsignal) on a variety of computer-readable transmission mediums,including wireless-based and wired/cable-based mediums, and may take avariety of forms (e.g., as part of a single or multiplexed analogsignal, or as multiple discrete digital packets or frames). Suchcomputer program products may also take other forms in otherembodiments. Accordingly, embodiments of the present invention may bepracticed with other computer system configurations.

In view of the embodiments described above, various related diagnosticand cutting performance methods may be provided to, among other things:determine an optimal or “maximum” cutting speed; determine an optimalabrasive material; determine an optimal abrasive mesh size; determine anoptimal abrasive flow rate; determine optimal orifice sizing; determinean optimal fluid pressure within a cutting system; determine the optimalsize of a mixing tube of a cutting system; and/or validate or optimizenew cutting system designs or new cutting head configurations.

Although an example workpiece 14 is shown in the Figures, a wide varietyof workpieces, having various material compositions, sizes, thicknesses,shapes, curvatures, and other characteristics, can be cut using thesystem 10. Similarly, while an example sample or coupon 52 is shown inthe Figures, a wide variety of coupons, having various materialcompositions, sizes, thicknesses, shapes, curvatures, and othercharacteristics, can be cut using the system 10. In many embodiments,the characteristics of the sample or coupon 52 can be selected so as togenerally match or be generally representative of those of the workpiece14 to be cut, or can be selected so that the forces imparted to thesample or coupon 52 by the jet 42 of the system 10 generally match orare generally representative of those expected to be imparted to theworkpiece 14 by the jet 42 of the system 10.

Moreover, aspects, features and techniques of the various embodimentsdescribed above can be combined to provide yet further embodiments. Allof the U.S. patents, U.S. patent application publications, U.S. patentapplications, foreign patents, foreign patent applications andnon-patent publications referred to in this specification and/or listedin the Application Data Sheet, including U.S. Provisional PatentApplication No. 62/234,499, filed Sep. 29, 2015, are incorporated hereinby reference, in their entirety. Aspects and features of the embodimentscan be modified, if necessary to employ concepts of the various patents,applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A method of improving fluid jetperformance, the method comprising: selecting a first setting for acharacteristic of a fluid jet system; forming a first cut in a coupon ofmaterial using the fluid jet system having the first setting for thecharacteristic; while forming the first cut in the coupon, measuring afirst history of reactive forces imparted by the fluid jet system to thecoupon during at least a portion of the first cut; selecting a secondsetting for the characteristic of the fluid jet system; forming a secondcut in the coupon using the fluid jet system having the second settingfor the characteristic; while forming the second cut in the coupon,measuring a second history of reactive forces imparted by the fluid jetsystem to the coupon during at least a portion of the second cut;designating the first setting as an optimal setting if an average ortypical value of the first history of reactive forces is lower than anaverage or typical value of the second history of reactive forces and aquality criterion of the first cut is acceptable; and designating thesecond setting as an optimal setting if the average or typical value ofthe second history of reactive forces is lower than the average ortypical value of the first history of reactive forces and a qualitycriterion of the second cut is acceptable.
 2. The method of claim 1,wherein the characteristic is a translation speed of a cutting head ofthe fluid jet system.
 3. The method of claim 1, wherein thecharacteristic is a size of a fluid jet orifice of the fluid jet systemwhich generates a fluid jet during operation to perform the first andsecond cuts.
 4. The method of claim 1, wherein the characteristic is afluid pressure developed within the fluid jet system immediatelyupstream of an orifice that generates a fluid jet during operation toperform the first and second cuts.
 5. The method of claim 1, wherein thecharacteristic is a type of an abrasive introduced into a fluid jetgenerated by the fluid jet system during operation to perform the firstand second cuts.
 6. The method of claim 1, wherein the characteristic isa mesh size of an abrasive introduced into a fluid jet generated by thefluid jet system during operation to perform the first and second cuts.7. The method of claim 1, wherein the characteristic is a flow rate ofan abrasive introduced into a fluid jet generated by the fluid jetsystem during operation to perform the first and second cuts.
 8. Themethod of claim 1, wherein the characteristic is a size of a mixing tubeof the fluid jet system from which a fluid jet is discharged duringoperation to perform the first and second cuts.
 9. The method of claim1, wherein the characteristic is a first characteristic, the optimalsetting is a first optimal setting, and the method further comprises:selecting a first setting for a second characteristic of the fluid jetsystem; forming a first supplemental cut in the coupon using the fluidjet system having the first setting for the second characteristic; whileforming the first supplemental cut in the coupon, measuring a firstsupplemental history of reactive forces imparted by the fluid jet systemto the coupon during at least a portion of the first supplemental cut;selecting a second setting for the second characteristic of the fluidjet system; forming a second supplemental cut in the coupon using thefluid jet system having the second setting for the secondcharacteristic; while forming the second supplemental cut in the coupon,measuring a second supplemental history of reactive forces imparted bythe fluid jet system to the coupon during at least a portion of thesecond supplemental cut; designating the first setting for the secondcharacteristic as a second optimal setting if an average or typicalvalue of the first supplemental history of reactive forces is lower thanan average or typical value of the second supplemental history ofreactive forces and a quality of the first supplemental cut isacceptable; and designating the second setting for the secondcharacteristic as a second optimal setting if the average or typicalvalue of the second supplemental history of reactive forces is lowerthan the average or typical value of the first supplemental history ofreactive forces and a quality of the second supplemental cut isacceptable.
 10. The method of claim 9 wherein: the first characteristicincludes one of: a translation speed of a cutting head of the fluid jetsystem; a size of a fluid jet orifice of the fluid jet system whichgenerates a fluid jet; a fluid pressure developed within the fluid jetsystem immediately upstream of the fluid jet orifice; a type of anabrasive introduced into the fluid jet; a mesh size of an abrasiveintroduced into the fluid jet; a flow rate of an abrasive introducedinto the fluid jet; and a size of a mixing tube of the fluid jet systemfrom which the fluid jet is discharged; and the second characteristicincludes another of: the translation speed of the cutting head of thefluid jet system; the size of the fluid jet orifice of the fluid jetsystem which generates the fluid jet; the fluid pressure developedwithin the fluid jet system immediately upstream of the fluid jetorifice; the type of an abrasive introduced into the fluid jet; the meshsize of an abrasive introduced into the fluid jet; the flow rate of anabrasive introduced into the fluid jet; and the size of the mixing tubeof the fluid jet system from which the fluid jet is discharged.
 11. Themethod of claim 9, wherein the first supplemental history of reactiveforces is a history of net force imparted by the fluid jet system to thecoupon.
 12. The method of claim 9, wherein the first supplementalhistory of reactive forces is a history of a horizontal component of anet force imparted by the fluid jet system to the coupon.
 13. The methodof claim 9, wherein the first supplemental history of reactive forces isa history of a vertical component of a net force imparted by the fluidjet system to the coupon.
 14. The method of claim 1, wherein the firsthistory of reactive forces is a history of net force imparted by thefluid jet system to the coupon.
 15. The method of claim 1, wherein thefirst history of reactive forces is a history of a horizontal componentof a net force imparted by the fluid jet system to the coupon.
 16. Themethod of claim 1, wherein the first history of reactive forces is ahistory of a vertical component of a net force imparted by the fluid jetsystem to the coupon.